Refrigerant flow control including refrigerant agitation



April 25, 1967 w E. CLARK ETAL REFRIGERANT FLOW CONTROL INCLUDING REFRIGERANT AGITATION Filed Feb. 16, 1966 FIG. 2

INVENTORS.

E. CL AR K.

CHECK.

WILLIAM DONALD wfi - ATTORNEY.

a United States Patent 3,315,485 REFRIGERANT FLOW CONTROL INCLUDING REFRIGERANT AGITATION William E. Clark, Syracuse, N.Y., and Donald R. Check, Minneapolis, Minn., assignors to Carrier Corporation, Syracuse, N.Y., a corporation of Delaware Filed Feb. 16, 1966, Ser. No. 527,868 4 Claims. (Cl. 62-218) This invention relates broadly to a refrigeration machine. More particularly, this invention relates to control of refrigerant'flow in a refrigeration machine. Still more particularly, this invention relates to a liquid refrigerant metering device particularly equipped to pass a mixture of liquid and gaseous refrigerant to the evaporator of a refrigeration machine at low load conditions to improve the efliciency of the evaporator at low load.

In high tonnage refrigeration machines, a compressor is arranged to extract gaseous refrigerant from an evaporator, compress the refrigerant, and pump it to a condenser where it is cooled and condensed. In communication with the condenser, there is normally provided a receiver for collecting liquid refrigerant formed in the condenser prior to its passage to the evaporator. The receiver usually contains refrigerant both in the liquid and gaseous phases and flow from the receiver is regulated by a float operated valve mechanism.

Under normal operating conditions, the level of the liquid refrigerant collected in the receiver is a function of the pressure difference between the high pressure side of the machine and the low pressure side of the machine and the load on the machine, it being understood the condenser and receiver are disposed in the high pressure side and the evaporator in the low pressure side of the machine. Refrigerant flow from the high side to the evaporator occurs in an amount related to the loading on the machine and automatic controls such as suction guide vanes are provided for the purpose of maintaining flow rates corresponding to machine loading. Float operated valve assemblies are designed to pass a predetermined arnount of refrigerant in accordance with the level of liquid refrigerant collected to maintain a liquid seal in the receiver.

The liquid from the receiver is passed through the float valve to the evaporator. The evaporator contains a multiplicity of tubes usually referred to as tube bundles through which the medium to be cooled by the machine is passed in heat transfer relation with the refrigerant in the evaporator. Under normal operating conditions, the heat supplied to the refrigerant from the medium being cooled is suflicient to cause the liquid refrigerant in the evaporator to boil vigorously. The boiling refrigerant thus wets all the tubes in the evaporator, providing optimum heat transfer between the medium and the refrigerant. However, at low loads, a relatively small quantity of heat is given off by the medium. The refrigerant, under these conditions, does not boil vigorously enough to wet all the tubes particularly those in the upper rows of the bundle, causing the efliciency of the evaporator to decrease. Therefore, to maintain evaporator efiiciency at low load, the liquid refrigerant therein must be agitated. To accomplish this, a portion of the high pressure gaseous refrigerant from the condenser is passed through the pool of liquid refrigerant in the evapoartor.

The chief object of this invention is to provide a simplified refrigerant flow control for passing both liquid and gaseous refrigerant to the evaporator. It is an additional object of this invention to provide a refrigerant control device which will maintain a liquid seal in the condenser under normal operating conditions. A further object of this invention is to provide a control for passing liquid and gaseous refrigerant to the evaporator to provide agitation of the liquid refrigerant therein under low load conditions.

The objects of this invention are attained by providing a cylinder having one end in communication with the interior of the receiver. A control line is provided between the other end of the cylinder and the evaporator. A valve in said line responsive to an operating characteristic of the refrigeration machine is provided to open the line under low load conditions. A piston disposed Within the cylinder is operably connected to a refrigerant metering float valve, preferable by a flexible cable or chain. When the control line valve is opened due to low load conditions, the pressure differential across said piston will cause it to be displaced toward the end of the cylinder in communication with the evaporator. This will hold the float valve open a predetermined amount to pass liquid therethrough causing agitation of the collected liquid refrigerant in the evaporator.

Other objects and features of this invention will be apparent upon consideration of the ensuing specification and drawings in which:

FIGURE 1 is a somewhat schematic view of a refrigeration machine wherein the evaporator-condenser section is shown in sectional elevation, incorporating a control mechanism illustrating the invention.

FIGURE 2 is a fragmentary view of the receiver portion of a refrigeration machine illustrating the float valve and agitator mechanism.

Referring more particularly to the drawing there is shown a centrifugal refrigeration machine 1 for cooling a large quantity of water. Refrigeration machines of this type are employed to cool water flowing within a closed circuit forming a part of an air conditioning installation. The machine 1 having a refrigerant motor compressor 2 includes a shell 3 for housing the heat transfer units (evaporator and condenser) associated 'with the machine. The shell 3 has a partition 4 therein for separating the high pressure condenser section 5 from the low pressure evaporator section 6. A tube 'bundle 7 in evaporator section 6 is provided for passing the water to be chilled therethrough.

Refrigerant receiver or float box 8 is provided for receiving gaseous and liquid refrigerant from the condenser through opening 9 communicating therewith. Float valve assembly 10 in float box 8 is provided for metering refrigerant from the float box to the evaporator section 6 through passageway 9'. The float valve assembly 10 comprises float ball 11, float arm 12, stiffening member 13, and throttle plates 14. The float valve assembly is pivoted on pin 15 mounted in the sides of opening 14' formed in the receiver. A cylinder 16 is provided having one end 16' thereof in communication with the interior of float box 8 and the other end 16" in communication with evaporator 6 through control line 17. Control line valve 18 is provided in control line 17. Solenoid 19 is provided to actuate valve 18 under low load conditions in response to a refrigeration machine operating characteristic such as guide vane position. Therefore, under low load conditions cylinder 16 is in communication with evaporator 6. A piston 20 in cylinder 16 is operably connected by chain or cable 21 to float valve stiffening member 13. A spring 21 is provided to bias piston 20 toward the float valve assembly 10.

Considering the operation of this control system under normal operating conditions, valve 18 is closed. Leakage between the cylinder 16 and piston 20 will cause an equalization of pressure on both sides of piston 20. Piston 20, under the force of spring 21 is therefore disposed toward the end 16' of cylinder 16. In this position, the cable 21 will not interfere with the normal operation of float 'to decrease in the evaporator.

' heat given off by the water the refrigerant comprising:

, 3 I valve assembly 10. As such, float valve assembly 10 will maintain a constant liquid refrigerant level in float box 8. Under low load conditions refrigerant volume will tend However, float valve assembly 10 will still operate to maintain a liquid seal in float box 8. In order to do so, float valve assembly 10 will be substantially closed and How of refrigerant to the Under these conditions, the being cooled will be insuflicient to boil the collected refrigerant in the evaporator. The upper tubes of the tube bundle will not be wetted by evaporator will be minimal.

the refrigerant and the efliciency of' the evaporator will decrease.

' To maintain the efficiency of the evaporator at a' high 7 level, it is desirable to pass both liquid and gaseous refrigerant to the evaporator to cause agitation of the liquid therein to wet all the tubes of the tube bundle. To accomplish' this, the float valve assembly 10 is opened to allow all of the liquid collected therein and gaseous refrig erant to pass through passageway 9' into the evaporator. By actuating solenoid 19 in response to an operating condition of the refrigeration machine indicative of low load conditions such as compressor inlet guide vane position, valve 18 will be opened thereby subjecting piston 20 to the pressure differential between the high pressure condenser section 5 and the low pressure evaporator section 6. This will cause piston 20 to movetoward end 16" of the cylinder. 16, opening float valve assembly 10 a predetermined arnount causing'the liquid in the float box 8 to be drained therefrom, breaking the liquid seal therein. Both liquid and gaseous refrigerant will then flow to the evaporator to agitate the collected liquid refrigerant there- While we have described a preferred embodiment of "our invention, it is to be understood that the invention is .not limited thereto but may be otherwise embodied within the scope of the following claims.

We claim: a 1. A refrigerant'flow control device for varying, the

v position of a refrigerant metering float valve in the high pressure side of a refrigeration machine irrespective of level therein under low load conditions refrigeration machine indicative of low load condi- 'tions to provide low side pressure to the end of said cylinder opposite the end in communication with the high pressure side of the machine.

2. A refrigerant flow control device according to claim 1 wherein said flexible means operably connecting said piston to the float valve is a cable. 7

3. A refrigerant flow control device according to claim 1 wherein said means to provide low side' pressure to the end of said cylinder opposite'the end in communication with the high pressure side of the refrigeration machine comprises:

a control line having with the evaporator section of the refrigeration machine,

a valve disposed in said line to open or close the line,

and a, 7

means operable in actuate said valve.

4. A refrigerant flow control device according to claim 3 wherein said means to actuate said valve is a solenoid.

References Cited by the Examiner UNITED STATES PATENTS 2,068,249 1/1937 Terry 62 -218 X 2,581,330 1/1952 Patterson 62509 x 2,667,756 2/1954 Atchison 62 -174 LLOYD L. KING, Primary Examiner.

one end in communication with said cylinder and the other end in communication response to low load conditions to 

1. A REFRIGERANT FLOW CONTROL DEVICE FOR VARYING THE POSITION OF A REFRIGERANT METERING FLOAT VALVE IN THE HIGH PRESSURE SIDE OF A REFRIGERATION MACHINE IRRESPECTIVE OF THE REFRIGERANT LEVEL THEREIN UNDER LOW LOAD CONDITIONS COMPRISING: A PNEUMATIC CYLINDER IN THE HIGH PRESSURE SIDE OF THE REFRIGERATION MACHINE HAVING ONE END IN COMMUNICATION WITH THE HIGH PRESSURE SIDE OF THE MACHINE, A PISTON SLIDABLY DISPOSED IN SAID CYLINDER, 